Abstract
New empirical formulas are proposed for the specific sediment deposition and the annual storage deposition rate of which reasonable prediction is required in estimating the design sediment deposition of a reservoir.First, 122 data on the sediment deposition measured up to the year 1971 were gathered from all reservoirs in Japan to compute the average specific sediment deposition qs and the average annual storage deposition rate rs (%).On the other hand, the following seven factors were adopted as deposition-governing ones which are easy in gathering in planning a reservoir and which are measurable, and gathered for analysis from every reservoir:
F: Drainage area (km2)
C: Reservoir capacity (total capacity at the beginning of project, in 103m3)
Y: Length of record from the date of completion (period from the date of completion to the year 1971, in years) P: Average annual rainfall (annual rainfall averaged over the period Y, in mm/year)
P24: Maximum daily rainfall (maximum daily rainfall averaged over the period Y, in mm/day)
Qmax: Maximum flood discharge (maximum flood discharge for the period Y, in m3/sec)
Rf: Average relief (difference in height, within a 16-km2 mesh on a 1/50000-scale map, averaged arithmetically over all the basin, in m)
Using the above materials for analysis, a product model was formulated as a relation between the specific sediment deposition qs or the annual storage deposition rate rs and each explanative variable, and the multiple regression analysis method was applied to each of reservoir-capacity classes (49 reservoirs for the case C<107m3 and 73 reservoirs for the case C<107m3) to derive new eight empirical formulas (Eqs.1-8) for obtaining qs or rs.Values calculated from these formulas were compared with measured values.As is shown in Figs.1-4, equations 1, 4, 6 and 7 show comparatively good adaptability. Therefore, these new empirical formulas seem to be useful for estimating the design sediment deposition of a reservoir in its planning.
